This invention relates generally to power transmission electronics and in particular to measuring and using the real-time impedance of a power line used for transmission of electrical power.
Electrical power is carried over the grid to consumers by a network of power lines. These power lines span various types of terrain and experience a wide variety of ever-changing environmental conditions, and the lines themselves vary in their materials and construction. Not only are the operating conditions constantly changing, the power transmitted via power lines also changes based on the supply and demand for the power. This causes variations in the temperature of these lines, which tend to sag (and thus increase in length and decrease in cross sectional area) when their temperature increases. For these reasons, power lines generally have dynamically changing properties, such as impedance, which variably affect their performance over time.
One important characteristic of a power line is its ampacity, which is a measurement of an amount of electric current that the power line can carry under specified temperature limitations and within a specified environment. The ampacity of a power line is based on many factors, including the physical and electrical properties of the conductor, as well as the temperature, wind, and other environmental conditions surrounding the power line. As the properties of a power line (e.g., impedance) change, the ampacity also changes. Currently, power transmission systems fail to take into account all of the important dynamic properties of a power line, which leads to the underutilization of the power lines. This can be a significant problem if the power lines are congested, where the lines are operating at or near their maximum. In the United States, for example, the cost of congestion in power lines may exceed $8 billion per year. The cost of supplying power increases in congestion cases, since power has to be purchased from generators located closer to the load, and hence at higher costs. Accordingly, a significant savings can be achieved each year by increasing the ampacity of congested power lines.
Accordingly, what are needed are techniques for determining accurate, real-time impedances for power lines, thereby allowing more accurate estimation of the properties of a power line (such as ampacity). This would enable many benefits, including more efficient use of power lines, as well as detecting faults and determining the stability of a power line.